The present application claims priority to Japanese Application No. P10-336027 filed Nov. 26, 1998 which application is incorporated herein by reference to the extent permitted by law.
1. Field of the Invention
The present invention relates to a gel electrolyte containing fibrous insolubles and a gel-electrolyte battery incorporating the gel electrolyte.
2. Description of the Related Art
In recent years, portable electronic apparatuses including camcorders (VTR) portable telephones and portable computers have come on the market. An attempt has been made to reduce the size and weight of the foregoing electronic apparatuses.
As the portable power sources for the foregoing electronic apparatuses, batteries, in particular, secondary batteries, and more particularly lithium batteries have been energetically researched and developed to reduce the thickness of the battery and to realize a foldable structure. As the electrolyte for the above-mentioned batteries, solid electrolytes manufactured by solidifying an electrolyte have energetically been studied. In particular, attention is being given to a solid electrolyte (hereinafter called a xe2x80x9cgel electrolytexe2x80x9d) containing a polymer compound.
As a plasticizer adaptable to the gel electrolyte, an electrolyte has been employed which has been prepared by dissolving lithium salt, such as Lipf6, in a non-aqueous carbonate solvent of, for example, propylene carbonate (PC) or xcex3-butyrolactone. In the foregoing case, a gel electrolyte exhibiting a relatively high conductivity can be obtained. Thus, the foregoing structure has been expected to be put into practical use.
The non-aqueous solvent, such as PC or xcex3-butyrolactone, which is capable of improving-ion conductivity, however, deteriorates the mechanical strength of the gel electrolyte depending on the content of the non-aqueous solution. Hence, it follows that the cycle characteristic and reservation easiness of the lithium-ion battery deteriorate excessively. Further, an adverse influence is exerted on the characteristics of the battery including the discharge capacity.
Also, a gel electrolyte which does not incorporate the non-aqueous solvent, such as PC or xcex3-butyrolactone, encounters the foregoing problems if the glass transition point, the molecular weight of the matrix polymer contained in the gel electrolyte or the molecular weight Also, a gel electrolyte which does not incorporate the non-aqueous solvent, such as PC or xcex3-butyrolactone, encounters the foregoing problems if the glass transition point, the molecular weight of the matrix polymer contained in the gel electrolyte or the molecular weight is low similar to the plasticizer.
In an embodiment, the present invention provides a gel electrolyte comprising: a plasticizer having lithium salt; a matrix polymer for dispersing the plasticizer; and fibrous insolubles.
In view of the foregoing, an object of the present invention is to provide a gel electrolyte which is capable of improving the cycle characteristic of a lithium-ion battery and preservation easiness at high temperatures and a gel-electrolyte battery incorporating the gel electrolyte.
To achieve the foregoing object, according to one aspect of the present invention, there is provided a gel electrolyte comprising: a plasticizer containing lithium salt; matrix polymer for dispersing the plasticizer; and fibrous insolubles.
In an embodiment, the present invention provides a gel-electrolyte battery comprising: a positive-electrode-mix layer; a negative-electrode-mix layer; and a gel-electrolyte layer, wherein the gel-electrolyte layer is constituted by a gel electrolyte having a plasticizer which contains lithium salt, a matrix polymer for dispersing the plasticizer and fibrous insolubles.
The gel electrolyte and the gel-electrolyte battery according to the present invention have the structure in which the gel electrolyte constitutes the gel electrolyte layer having the fibrous insolubles. Therefore, the mechanical strength of the gel electrolyte and the gel electrolyte layer constituted by the gel electrolyte can be increased. Moreover, the cycle characteristic and preservation easiness at high temperatures can be improved.
Other objects, features and advantages of the invention will be evident from the following detailed description of the preferred embodiments described in conjunction with the attached drawings.